rpmsg: char: Add pr_fmt() to prefix messages

Make all messages to be prefixed in a unified way.
Add pr_fmt() to achieve this.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20211108135945.3364-1-arnaud.pouliquen@foss.st.comSigned-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/rpmsg/rpmsg_char.c

@@ -9,6 +9,9 @@
  * Based on rpmsg performance statistics driver by Michal Simek, which in turn
  * was based on TI & Google OMX rpmsg driver.
  */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
 #include <linux/cdev.h>
 #include <linux/device.h>
 #include <linux/fs.h>
@@ -550,7 +553,7 @@ static int rpmsg_chrdev_init(void)
 
 	ret = alloc_chrdev_region(&rpmsg_major, 0, RPMSG_DEV_MAX, "rpmsg");
 	if (ret < 0) {
-		pr_err("rpmsg: failed to allocate char dev region\n");
+		pr_err("failed to allocate char dev region\n");
 		return ret;
 	}
 
@@ -563,7 +566,7 @@ static int rpmsg_chrdev_init(void)
 
 	ret = register_rpmsg_driver(&rpmsg_chrdev_driver);
 	if (ret < 0) {
-		pr_err("rpmsgchr: failed to register rpmsg driver\n");
+		pr_err("failed to register rpmsg driver\n");
 		class_destroy(rpmsg_class);
 		unregister_chrdev_region(rpmsg_major, RPMSG_DEV_MAX);
 	}